This invention relates generally to an archery device and, in particular to a hand held trigger release mechanism for improving accuracy.
Devices for helping an archer draw and fire a conventional bow have been used for some time. Typically, these devices are hand held units that releasably engage the bowstring so that the archer can draw the bow to a firing position using a hand grip rather than a finger grip. The bowstring is released or fired by operation of a finger actuated trigger.
In U.S. Pat. No. 4,009,703 to Cunningham there is disclosed a hand held unit wherein the bowstring is secured within a circular housing by means of a latched cam. The latching force for holding the cam latched is provided by the bowstring tension which is exerted directly on the cam. Actuating the trigger pulls the latch back against the tension of the bow. As can be seen, the triggering force needed to fire the bow can change drastically each time the bow is fired. Accordingly, the archer is never sure when release will occur and his accuracy is adversely affected.
One other problem that is inherent in many prior art release mechanisms involves the natural reaction of the bowstring to return directly to its normal untensioned position when released. Any spin or lateral displacement imparted to the string at the time of release will produce an unwanted reaction in the string which results in reduced accuracy. The trigger release shown in the above noted Cunningham patent employs a rotatable release cam that physically moves across the bowstring before release causing the string to be released in a twisted condition. Similarly, the Cunningham trigger is arranged to be actuated by the archer depressing his thumb in a direction that is oblique to the intended line of flight of the arrow. Pushing the trigger in this manner against the high holding force exerted by the bowstring invariably causes the hand to move during release disturbing the trajectory of the arrow.
In U.S. Pat. No. 4,083,348 to Fletcher, there is disclosed a bow drawing and release mechanism that overcomes some of the problems found in the prior art. Fletcher utilizes a flexible cord to engage and hold the bowstring during draw. The cord encircles the bowstring and is looped over a rotatable latch that forms part of the triggering mechanism. When the latch is released at firing, the cord, having greater flexibility than the taut bowstring, falls away from the string without imparting a spin thereto. The trigger of the Fletcher device is also arranged to be pulled rearwardly in a direction generally parallel to the intended flight of the arrow. This, in turn, reduces the tendency of the archer to turn his hand at release and results in improved accuracy.
The Fletcher device, like that described by Cunningham, however, employs the bow tension to hold the triggering mechanism in a cocked position. Because the triggering mechanism is directly coupled to the tensioned bow, actuation of the trigger is adversely affected by this unwanted and highly irregular force. The tension of the bow at the moment of firing can change between each draw and the archer is never sure when the trigger will release the bowstring. This uncertainty as to the exact moment of fire adversely affects accuracy. Furthermore, it is not possible to adjust the triggering mechanism with any degree of accuracy to obtain release of the bow repeatedly at a desired trigger pressure. The release pressure of the triggering mechanism must be set while the bow is actually being drawn. This makes adjusting the trigger extremely difficult particularly under field conditions.
The Fletcher trigger mechanism relies upon an over center linkage to withstand the direct bow tension during draw. Any slight misalignment of this linking through mishandling or misadjusting of the device, can produce premature firing of the arrow and thus pose a potential danger to the user or others close by.